Glossary · also called Automatic Power Factor Control panel, Automatic Power Factor Correction panel, APFC, PF correction panel
What is an APFC Panel (Automatic Power Factor Control)?
APFC panel: An APFC panel (automatic power factor control panel) is an electrical panel that keeps a facility's power factor close to a set target by switching capacitor banks in and out in steps. A power factor controller measures the load through a current transformer and operates capacitor-duty contactors or thyristor switches as the load changes.
Definition
Motors, transformers and other inductive loads draw reactive power, which lowers power factor. Low power factor means higher current for the same useful power, more losses and, under many Indian electricity tariffs, higher bills — some utilities apply power factor penalties or incentives, and others bill on kVAh, where poor power factor directly increases billed energy. Check your own tariff.
Capacitors supply reactive power locally. Because the load varies through the day, a fixed capacitor bank would over- or under-correct. An APFC panel solves this by dividing the capacitance into steps and switching them automatically.
How it works
Main components:
- Power factor controller (APFC relay) that measures PF through a CT and decides which steps to switch.
- Capacitor banks in steps, for example 25 kVAr and 50 kVAr units.
- Switching: capacitor-duty contactors, or thyristor switches for loads that change quickly.
- Detuned reactors in series with capacitors where harmonics are present, for example from VFDs.
- Protection: MCCBs or fuses per step, plus an incomer.
A sizing example, with illustrative figures only: a 400 kW load at 0.80 PF corrected to 0.98.
- Required kVAr = kW × (tan φ1 − tan φ2) = 400 × (0.750 − 0.203) ≈ 219 kVAr.
- A practical bank might be 225 kVAr: 1 × 25 kVAr plus 4 × 50 kVAr steps.
Each step becomes a group of lines in the panel BOM.
Common mistakes
- Ignoring harmonics. Plain capacitors on a site with many drives can fail early or cause resonance.
- Steps too coarse, so the controller hunts or cannot reach the target at light load.
- Standard contactors instead of capacitor-duty contactors, which handle inrush current.
- Over-correction to a leading power factor.
APFC panels are often supplied alongside an MCC panel or PCC. Check the correct HSN code and applicable GST rate for the panel you invoice.
In Zaptiz
Zaptiz Electrical includes an APFC template in its BOM Generator, with brand tiers, charges and margin, and can build the BOM from a PDF or image drawing or a photo of an existing panel for you to review.